As-cast　austenitic-bainite　nodular　iron　by　permanent　mold　casting　was　annealing　treated.　The　effects　of　annealing　treatment　on　microstructure　and　properties　of　the　nodular　iron　were　studied　using　orthogonal　test.　The　results　show　that　annealing　treatments　have　no　effect　on　graphite　morphology,　but　can　change　the　type　of　bainite.　The　strength,　ductility　and　toughness　of　the　nodular　iron　can　be　improved　significantly　by　annealing　treatment　at　low　temperature　and　meanwhile　its　hardness　are　not　reduced　obviously.　Its　strength　can　reach　about　1080MPa.